Suspended type centrifugal separator

ABSTRACT

A centrifugal separator having as its drive source a steam turbine comprising a first turbine rotor rotated in the normal direction and a second turbine rotor rotated in the reverse direction which are mounted on a turbine shaft, said second turbine rotor being driven to impart a reverse torque to the centrifugal separator when rapid deceleration of said centrifugal separator is required.

United States Patent I 1191 Nishimura et al.

[ Dec. 31, 1974 SUSPENDED TYPE CENTRIFUGAL 2,752,044 6/1956 OICOIt 210/368 x 2,779,475 1/1957 Olcott 210 368 X SEPARATOR 3,077,781 2/1963 Silver 73/465 Inventors: Shim Nishimura, y Kisaburo 3,734,399 5/1973 Oas 233/24 x Ishihama, Mitaka, both of Japan [73] Assignee: Shin Nippon Machinery Co., Ltd., Primary Examiner-Roy Lake k 0 J an Assistant Examiner-Craig R. Femberg y p Atto ey Age t 0 Firm Armstrong Nikaido & rn s n 9 r 9 [22] Filed. Mar. 30, 1973 wegnar [21] Appl. No.: 346,293

[57] ABSTRACT [52] Cl 210/138 73/512 210/368 A centrifugal separator having as its drive source 21 233/24 steam turbine comprising a first turbine rotor rotated [51] f- 301d 21/26 1304b 9/06 1304b 13/00 in the normal direction and a second turbine rotor ro- [58] Fleld of Search 210/89 368; 60/102, tated in the reverse direction which are mounted on a 60/333 335, 340; 415/123 152; 188/292 turbine shaft, said second turbine rotor being driven to 296; 290/52; 73/465, 512; 233/23 24 impart a reverse torque to the centrifugal separator when rapid deceleration of said centrifugal separator [56] References Cited is required UNITED STATES PATENTS 5 Cl 4 D F 752,545 2/1904 Goede et al. 60/102 rawmg gums I /2 l3 J 2\ /7 I 1 20 7 1 1 4 1- 4 A! no 4 ea 2 E 2 PATENTEDUEEB 1 I974 4 3,857,783

' SHEET 10 2 SUSPENDED TYPE CENTRIFUGAL SEPARATOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a suspended type centrifugal separator, and more specifically to a suspended type centrifugal separator driven by a steam turbine.

2. Description of the Prior Art Suspended type centrifugal separators have been widely used in various industries such as sugar, salt and pharmaceutical industries, but the conventional centrifugal separators of the type described have been driven by electric motors. In a suspended type centrifugal separator, a cycle of operation is repeated which generally consists of several steps of starting, charging materials, separating the materials, discharging the product and stopping. The period of this cycle of operation is extremely short and in addition, the speed of the centrifugal separator varies in the respective material charging, separating and product discharging steps. In case, for example, of the centrifugal separator used in the sugar industry, the separator is operated at 100 250 rpm. in the material changing step, at 1,000 1,500 r.p.m. in the separation step and at 30 60 r.p.m. in the product discharging step (sugar crystals scraping step), and one cycle of operation normally takes about 3 minutes. In order to satisfy such operating conditions, therefore, rapid speed control of the prime mover is necessary. Such speed control has been obtained in the conventional suspended type centrifugal separators by using a braking system in combination with the electric motor or by using a DC. variable speed electric motor. However, the use of the braking system is disadvantageous in that frequent replacement of brake shoes of the braking system is required, on the other hand the DC. variable speed electric motor is expensive and damageable. Recently, since the capacity of centrifugal separators has a tendency of becoming larger and larger, the use of electric motors for driving the separators is undesirable from the practical point of view, because they will also become large in size and complicated in construction. The present invention therefore proposes the use of a steam turbine as a prime mover in place of the conventionally used electric motors.

SUMMARY OF THE INVENTION The object of the present invention is to provide a suspended type centrifugal separator having as its drive source a steam turbine provided with braking means, by which the speed of the centrifugal separator can be controlled in accordance with the operation characteristics of said separator.

In order to attain the object set forth above, there is provided according to the invention a steam turbine driven suspended type centrifugal separator comprising in combination a suspended type centrifugal separator unit having a separator basket rotatable within a casing, a steam turbine unit consisting of a turbine casing, a turbine shaft rotatably supported in said turbine casing, a first turbine rotor fixedly mounted on said turbine shaft and rotated in the normal direction, a second turbine rotor fixedly mounted on said turbine shaft and rotated in the reverse direction, a first steam conduit for supplying pressurized steam to said first turbine rotor, a second steam conduit for supplying pressurized steam to said second turbine rotor, a first steam valve provided in said first steam conduit, a second steam valve provided in said second steam conduit and a steam exhaust port provided in the turbine casing, and a speed reducing mechanism through which the driving force of said steam turbine unitis transmitted to said separator basket.

The centrifugal separator according to the invention is advantageous in that surplus steam from the associated plant can be used for driving the steam turbine unit. Further, the steam turbine unit in the present invention is simple in construction and compact in size, and is ideally applicable for a large-sized suspended type centrifugal separator unit. Furthermore, the steam turbine unit according to the invention is highly conveniently used as a prime mover of suspended type centrifugal separators because it produces extremely large starting and braking torques as compared with electric motors, and said torques can be freely controlled.

For a better understanding of the invention, an embodiment of the invention will be described in detail hereunder with reference to the accompanying drawmgs:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of an embodiment of the steam turbine driven suspended type centrifugal separator according to the invention;

FIG. 2 is a plan view of the centrifugal separator;

FIG. 3 is a chart showing the rotating speed and driving force requirement of the centrifugal separator unit changing with time in one duty cycle of operation when the centrifugal separator of the invention is used in a sugar mill plant; and

FIG. 4 is a diagram illustrating how to put the suspended type centrifugal separator of the invention into automatic operation following to a predetermined schedule by controlling the turbine speed with a speed controller and an automatic timer.

DESCRIPTION OF THE PREFERRED EMBODIMENT Wirh reference to FIGS. 1 and 2, the suspended type centrifugal separator of the invention comprises a centrifugal separator unit 1 and a steam turbine unit 2. The separator unit 1 has a cylindrical casing 3 in which a cylindrical separator basket 4 is coaxially rotatably mounted on a vertical shaft 5. An arrangement is made such that in a material charging step a liquid containing a material, such as sugar crystals, to be separated is fedinto the casing 3 from a liquid storage tank 6 through a trough 7, and in a product discharging step the material deposited on the inner surface of the separator basket 4 is scraped off therefrom by a scraper or unloader 8 suspending vertically from a bracket 9 fixed on the casing 3. The liquid from which the material has been separated moves out of the separator basket 4 from the periphery of said basket and is discharged to the outside from a discharge port 10.

The steam turbine unit 2 has a turbine shaft 11 extending vertically through a casing 12. A turbine rotor 13 rotated in the normal direction (hereinafter referred to as normal turbine rotor) and another turbine rotor 14 rotated in the reverse direction (hereinafter referred to as reversing turbine rotor) are fixedly mounted on the turbine shaft 11 in the turbine casing 12, and a guide plate 15 is interposed between the two rotors which is fixed in the casing 12 and extending horizontally. Reference numeral 16 designates a conduit for supplying pressurized steam to drive the normal turbine rotor 13; 18 a conduit for supplying pressurized steam to drive the reversing turbine rotor 14', and 17 a steam exhaust port common for both turbine rotors. The steam supply conduits 16, 18 respectively are provided therein with steam valves 27, 29 which are operated automatically by a speed control system to be described later. On the lower end of the turbine shaft 11 extending downward from the casing 12 is fixedly mounted a gear 19 which is meshing with a gear 20 fixedly mounted on a rotary shaft 21, said gears 19 and 20 constituting a speed reducing mechanism. The rotary shaft 21 is connected to a rotary shaft of the separator basket 4 by a suitable coupling. Reference numeral 22 designates an oil pump for supplying lubricating oil to the bearings of the turbine shaft 11 and shaft 21, and 23 designates a cover plate provided centrally of the bottom plate of the separator basket 4 to close the product discharge port, said cover plate being shown as removed from said discharge port in FIG. 1.

The suspended type centrifugal separator of the invention constructed as described above starts operation when the steam valve 27 in the steam supply conduit 16 is opened. The pressurized steam supplied from the conduit 16 drives the normal turbine rotor 13 and discharges from the exhaust port 17 with a reduced pressure. The rotation of the turbine shaft 11 is reduced to the speed determined by a gear ratio of the gears 19, 20 and transmitted to the separator bracket 4. lt will be obviously understood that the rotating speed of the separator basket 4 can be varied by changing the degree of opening of the steam valve 27. Where it is required to reduce rapidly the rotating speed of the separator basket, the steam valve 27 is closed and concurrently the steam valve 29 is opened. ln this case, the pressurized steam from the steam supply conduit 18 is supplied to the reversing turbine rotor 14 giving a reversing torque the turbine shaft 1 1 being rotated in the normal direction by inertia, to reduce the speed rapidly. As described, the steam turbine unit 2 according to the invention is capable of accelerating or decelerating the separator basket 4 freely by the controlled operations of the steam valves 27, 29, and the starting torque or braking torque produced thereby is extremely larger than those by an electric motor. Therefore, the steam turbine unit is highly effectively used as a driving source of the suspended type centrifugal separator for which frequent change in speed is required with short intervals.

The chart of HO. 3 shows the variations in the rotating speed and driving force of the suspended type centrifugal separator of the invention which is operated in a sugar mil] plant under the conditions that the maximum speed is l,500 r.p.m., the driving force is 100 KW, and the period of one duty cycle is 3 minutes. In the chart, reference character a indicates the starting point of the separator; the time b-c indicates a material charging period; the time c-d-e indicates a separation period; the time e-f indicates a deceleration period; the time f-g indicates a product discharging period; h indicates the stopping point of the separator; the dotted line indicates the driving force; and the solid line indicates the rotating speed. The section in which the dotted line lies below the axis of abscissa indicates the period in which braking is in effect, namely the reversing turbine rotor is in operation.

FIG. 4 shows a system of automatic speed control as given in FIG. 3 for a steam turbine driven suspended type centrifugal separator. The system includes a timer box 24 and a control box 25. In the timer box are incorporated a normal turbine rotor starting timer 31, a charging operation timer 32, a separation operation timer 33, a normal turbine rotor stopping timer 34, a reversing turbine rotor starting timer 35, a discharge operation timer 36 and a normal turbine rotor stopping timer 37. These timers are actuated sequentially upon passage ofa time set in the individual timer. In the control box 25 is incorporated the Woodward electric or hydraulic control device known in the art which during operation of the separator receives a signal from each timer and generates a set voltage corresponding to said timer. On the other hand, a tachometer 28 is connected to the turbine shaft 11 and a voltge proportional to the rotating speed of the turbine shaft detected by said tachometer is transmitted to the control box 25 wherein the difference in voltage between said voltage and the aforesaid set voltage is amplified to act the actuator of the steam valve 27. The actuator stops its operation when the voltage difference becomes zero, setting the steam valve 27 in position to give a predetermined speed of rotation corresponding to the timer in operation. In the manner described, when the charging operation timer 32 is in operation, for example, the separator is operated at the charging speed of 200 r.p.m. and then accelerated to the highest separation speed of 1,500 r.p.m. when the separation operation timer 33 is actuated and operated continually at said speed until the time set in said timer 33 elapses. Now, when the timer 34 is actuated, the timer 35 is actuated concurrently and the steam valve 27 is closed and the steam valve 29 opened, so that the separator is braked by the reversing turbine rotor as described above. The open ing of the steam valve 29 is effected not by the control of the control box 25 but by an actuator electrically connected directly to the timer 35. The steam valve 29 may be replaced by an electrically operative valve which operates in response to an electric signal supplied from the timer 35. The ateam valve 29 is closed by the action of a limit switch which is actuated at the point when the speed of the separator, indicated on the tachometer 28, has dropped to a level slightly above the discharging speed, e.g., 4O r.p.m. or, for example, to r.p.m. Thereafter, the timer 36 is actuated at the point when the tachometer 28 indicates the separator running at the discharging speed, e.g., 4O r.p.m.,

whereby the steam valve 27 is set and held in an open position corresponding to the discharging speed throughout the period of time set in said timer.

Although the present invention has been described and illustrated herein in terms of a specific preferred embodiment thereof, it will be obvious to those skilled in the art that opening and closing of the steam valves may be effected manually without using the timers, by pushing buttons which will be provided on the control box in lieu of said timers, and it should also be understood that many other modifications and changes are possible within the scope of the invention set forth in the appended claims.

We claim:

1. A steam turbine driven suspended type centrifugal separator comprising in combination a suspended type centrifugal separator unit having a separator basket rotatable within a casing, a speed reducing mechanism and a steam turbine means wherein said steam turbine means drives said separator basket through said speed reducing mechanism such that the speed thereof varies in accordance with a predetermined pattern with respect to time during short cycles said steam turbine means comprising a turbine casing, a turbine shaft rotatably supported in said turbine casing, a first turbine rotor fixedly mounted on said turbine shaft and rotated in the normal direction, a second turbine rotor fixedly mounted on said turbine shaft and rotated in the reverse direction, a first steam conduit for supply pressurized steam to said first turbine rotor, a second steam conduit for supplying pressurized steam to said second turbine rotor, a first steam valve provided in said first steam conduit, a second steam valve provided in said second steam conduit and a steam exhaust port provided in the turbine casing, an actuator for operating said first steam valve, means for generating a set of voltages varying in accordance with said predetermined speed pattern of said centrifugal separator unit, means for sequentially selecting one of said set of voltages, means for detecting the speed of the centrifugal separator, means for generating a voltage proportioned to the detected speed, and means for generating a voltage proportional to the instantaneous difference between said selected one of said set of voltages and said voltage proportional to the detected speed, said actuator being operative in response to said voltage difference for controlling said first steam valve.

2. A steam turbine driven suspended type centrifugal separator as claimed in claim 1, wherein said selecting means includes a series of timers which are actuated in sequence.

3. A steam turbine driven suspended type centrifugal separator as claimed in claim 2, wherein said selecting means includes in said series of timers a timer which commands the operation of said second steam valve.

4. A steam turbine driven suspended type centrifugal separator as claimed in claim 3, wherein there is provided means for closing said second steam valve when the speed of the separator has dropped to a predetermined level.

5. A steam turbine driven suspended type centrifugal separator as claimed in claim 4, wherein said second steam valve is an electrically operative valve. 

1. A steam turbine driven suspended type centrifugal separator comprising in combination a suspended type centrifugal separator unit having a separator basket rotatable within a casing, a speed reducing mechanism and a steam turbine means wherein said steam turbine means drives said separator basket through said speed reducing mechanism such that the speed thereof varies in accordance with a predetermined pattern with respect to time during short cycles said steam turbine means comprising a turbine casing, a turbine shaft rotatably supported in said turbine casing, a first turbine rotor fixedly mounted on said turbine shaft and rotated in the normal direction, a second turbine rotor fixedly mounted on said turbine shaft and rotated in the reverse direction, a first steam conduit for supply pressurized steam to said first turbine rotor, a second steam conduit for supplying pressurized steam to said second turbine rotor, a first steam valve provided in said first steam conduit, a second steam valve provided in said second steam conduit and a steam exhaust port provided in the turbine casing, an actuator for operating said first steam valve, means for generating a set of voltages varying in accordance with said predetermined speed pattern of said centrifugal separator unit, means for sequentially selecting one of said set of voltages, means for detecting the speed of the centrifugal separator, means for generating a voltage proportioned to the detected speed, and means for generating a voltage proportional to the instantaneous difference between said selected one of said set of voltages and said voltage proportional to the detected speed, said actuator being operative in response to said voltage difference for controlling said first steam valve.
 2. A steam turbine driven suspended type centrifugal separator as claimed in claim 1, wherein said selecting means includes a series of timers which are actuated in sequence.
 3. A steam turbine driven suspended type centrifugal separator as claimed in claim 2, wherein said selecting means includes in said series of timers a timer which commands the operation of said second steam valve.
 4. A steam turbine driven suspended type centrifugal separator as claimed in claim 3, wherein there is provided means for closing said second steam valve when the speed of the separator has dropped to a predetermined level.
 5. A steam turbine driven suspended type centrifugal separator as claimed in claim 4, wherein said second steam valve is an electrically operative valve. 